Not Applicable
Not Applicable
1. Field of the Invention
The invention relates to the manufacture of elastomeric tubes and rings. It is particularly concerned with a more efficient process for making lathe-cut rubber gaskets.
2. Background information
Lathe-cut rubber gaskets are widely used as jar rings and for sealing an automotive oil filter cartridge against a flange on an engine block. These gaskets have been made for many years by a labor-intensive process generally consisting of the following steps:
1) Extruding an uncured rubber tube and cutting it to a convenient length for handling on a mandrel (e.g., thirty inches).
2) Blowing the tube onto a curing mandrel and curing the rubber in a convection oven or an autoclave and thereby setting the internal diameter of the gasket;
3) Blowing the cured rubber tube off the curing mandrel and blowing it onto a grinding mandrel.
4) Grinding the outside of the tube to remove flats or bulges causing the tube to be out of specification for roundness, and also to set the external diameter of the gasket.
5) Blowing the tube off the grinding mandrel and blowing onto a cutting mandrel.
6) Forming a plurality of gaskets from each tube by using a lathe to cut the tube into rings of a predetermined length.
Other references of note in this area are:
U.S. Pat. No. 3,929,987 in which Holden et al. describe a process for making a flexible thermoplastic tube by coating a quasi-continuous mandrel made up of a number of interfitting segments. After forming the tube Holden et al. soften it by heating and then pull the continuous tube apart into segments.
U.S. Pat. No. 2,770,841, in which Cooke et al. describe a process for making and curing a continuous elastomeric tube having controlled ID and OD. Their cured tube is cut into rings.
U.S. Pat. No. 4,882,101 in which Ohkita et al. describe making reinforced rubber hose having controlled ID and OD by extruding the rubber over a continuous mandrel. Ohkita et al. use a plastic co-extruded mandrel that is chopped up and recycled when the hose is cut to length.
U.S. Pat. No. 4,174,365 in which Pahl describes both a mandrel that can be destroyed and recovered without cutting the hose and a machine for recirculating mandrels. Pahl""s arrangements allow for the fabrication of arbitrarily long hoses.
U.S. Pat. No. 4,104,098 (Hush et al.) and U.S. Pat. No. 4,512,912, (Babbin et al.) both show microwave curing (or partial curing) of extruded rubber hose.
A feature of the invention is a process for extruding rubber onto a series of spaced mandrels so as to form a segmented tube having precisely controlled internal and outer diameters, and for then cutting the tube into lathe-cut gaskets.
An advantage of a preferred embodiment of the invention is a reduction in the number of times a tube is blown onto or off of a mandrel in the process of making lathe-cut rubber rings. In a particular embodiment, a prior art process using five steps is replaced by a process using only two.
A feature of a preferred embodiment of the invention is the use of a non-contact diameter measurement means to determine the wall thickness of a tube extruded from a cross-head to yield a rubber tube having a precisely controlled outer diameter so that the grinding step of the prior art process can be at least reduced in extent and possibly avoided.
Another feature of a preferred embodiment of the invention is an arrangement for cutting a continuous tube, formed around a string of mandrels axially separated from each other by spacers, into tube segments by means that locate the spacers and make the cuts at the spacer locations.
Although it is believed that the foregoing recital of features and advantages may be of use to one who is skilled in the art and who wishes to learn how to practice the invention, it will be recognized that the foregoing recital is not intended to list all of the features and advantages. Moreover, it may be noted that various embodiments of the invention may provide various combinations of the hereinbefore recited features and advantages of the invention, and that less than all of the recited features and advantages may be provided by some embodiments.